I have heard two different time frames when Smith made the change from black to silver grip washers. One was in 1968 to 69. the other was late 71 to mid 1972.
I know that is kinda splitting hairs but if you were going to put a set of magna's on a 25, 27, 28, 29 it would seem to me if they weren't the ones numbered to the gun then a slightly earlier un numbered set would be better than a set several years newer than the revolver you were fitting.
So anyway, when did the change occur? Also did Smith do it to all frame sizes at the same time? Or is that something else to watch for?